#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<queue>
using namespace std;
const int N=500010;
int n,m,cnt,head[N],vis[N];//edge vis or not;
int ans=1,f1=1,f2=1;
priority_queue<int> q;
struct edge{
	int val,next,to;
}e[N<<1];
void add(int u,int v,int w){
	e[++cnt].next=head[u];
	head[u]=cnt;
	e[cnt].to=v;
	e[cnt].val=w;// 1,2->(i+1)/2
}
int z(int x){
	return (x+1)/2;
}
void init(){
	scanf("%d%d",&n,&m);
	for(int i=1;i<n;i++){
		int u,v,w;
		scanf("%d%d%d",&u,&v,&w);
		add(u,v,w);
		add(v,u,w);
		if(u!=1) f1=0;
		if(v!=u+1) f2=0;
		q.push(w);
	}
//	freopen("track.in","r",stdin);
//	freopen("track.out","w",stdout);
}
void dfs1(int cur,int len){
	for(int i=head[cur];i;i=e[i].next){
	//	cout<<"WTF"<<i<<" "<<cur<<" "<<len<<endl;
	//	system("pause");
		if(!vis[(i+1)/2]){
			vis[(i+1)/2]=1;
			dfs1(e[i].to,len+e[i].val);
		//	cout<<i<<" "<<e[i].to<<" "<<e[i].val<<" "<<len<<endl;
			vis[(i+1)/2]=0;
		}
	}
	ans=max(ans,len);
}
void dfs2(int cur,int len,int step){//len is the min length
	if(cur==n&&step==m){
		ans=max(ans,len);
		return;
	}
	if(cur==n||step==m) return;
	int l=0;
	for(int i=head[cur];i;i=e[i].next){
		l+=e[i].val;
		dfs2(e[i].to,min(len,l),step+1);
		dfs2(e[i].to,l,step);
	}
}
int main(){
	init();
	if(m==1){
		for(int i=1;i<=n;i++) dfs1(i,0);
	}else if(f1){
		ans=0;
		for(int i=1;i<=m;i++){
			if(q.empty()) break;
			ans+=q.top();
			q.pop();
			if(q.empty()) break;
			ans+=q.top();
			q.pop();			
		}
	}else if(m==n-1){
		int tmp;
		while(!q.empty()){
			tmp=q.top();
			q.pop();
		}
		ans=tmp;
	}else if(f2){
		dfs2(1,0,1);
	}
	printf("%d",ans);
	return 0;
}
/*
7 1
1 2 10
1 3 5
2 4 9
2 5 8
3 6 6
3 7 7

9 3
1 2 6
2 3 3
3 4 5
4 5 10
6 2 4
7 2 9
8 4 7
9 4 4

5 2
1 2 10
2 3 9
3 4 9
4 5 11
*/